#include <stdio.h>


int Fib(int n)
{
	int a = 1;
	int b = 1;
	int c = 1;
	while (n > 2)
	{
		c = a+b;
		a = b;
		b = c;
		n--;	
	   }   
	
	return c;
	
}





 int main()
  {
    int n = 0;
	scanf("%d",&n);
	int num = Fib(n);
	printf ("%d\n",num);
	return 0;	
  	
  }
